Solenoid pump

ABSTRACT

A solenoid pump for moving a fluid is disclosed. The pump includes a solenoid coil that generates an electromagnetic field for moving a plunger relative to a stationary core. Magnetic components of the solenoid pump direct the electromagnetic field to provide a substantially balanced magnetic force on the plunger.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under Title 35, U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 61/388,730, filed Oct. 1, 2010, entitled SOLENOID PUMP, the entire disclosure of which is hereby expressly incorporated by reference herein.

FIELD

The present invention relates to a fluid transfer pump, and more particularly to a solenoid pump for removing condensate water from an air conditioner.

BACKGROUND

Many solenoid pumps include a plunger moveable by an electromagnetic solenoid coil. Movement of the plunger displaces fluid through the solenoid pump. Solenoid pumps often include a pole piece configured to direct the electromagnetic field generated by the solenoid coil. The magnetic forces exerted by the electromagnetic field on the plunger are often unbalanced and non-uniform due to the shape of the pole piece. Magnetic gaps in the flux path for the electromagnetic field further contribute to inconsistent and non-uniform magnetic forces on the plunger. Off-axis magnetic forces may drag the plunger against the inner wall of the pump during pump operation. The increased friction in the travel path of the plunger leads to inefficient pump operation, power loss, increased wear to the parts of the pump, and increased noise during operation of the pump.

Many solenoid pumps have travel stops for limiting the travel of the plunger. Some pumps utilize an elastomeric washer or a wire compression spring as a travel stop for the plunger. In some pump designs, the interface between the plunger and the travel stops involves metal to metal contact which leads to greater operation noise and increased wear to parts of the pump.

SUMMARY

In an exemplary embodiment of the present disclosure, a solenoid pump is provided that comprises a body having a fluid inlet and a fluid outlet and a fluid conduit connecting the fluid inlet and the fluid outlet, a reciprocating member supported by the body and moveable along an axis between a first position and a second position, the reciprocating member moving fluid received from the fluid inlet on towards the fluid outlet during a movement between the first position and the second position, an electromagnetic coil configured to generate an electromagnetic field to move the reciprocating member from the first position to the second position, and a pole piece positioned radially outwardly from the coil for directing the electromagnetic field generated by the coil, the pole piece being substantially symmetrical relative to the axis to provide a substantially balanced magnetic force on the reciprocating member with respect to the axis.

In another exemplary embodiment of the present disclosure, a method of pumping a fluid is provided. The method comprises the steps of receiving fluid within a fluid conduit of a body through a fluid inlet, reciprocating a magnetic member supported by the body, to move the received fluid towards a fluid outlet of the body, and communicating the fluid outside of the body through the fluid outlet. The reciprocating step includes the steps of applying for a first duration a substantially balanced magnetic field towards the magnetic member to move the magnetic member from a first position in a first direction along an axis towards a second position to move a first portion of the received fluid towards the fluid outlet of the body, returning the magnetic member towards the first position in a second direction, the second direction being opposite the first direction, applying for a second duration the substantially balanced magnetic field towards the magnetic member to move the magnetic member in the first direction towards the second position to move a second portion of the received fluid towards the fluid outlet of the body, and returning the magnetic member towards the first position in the second direction.

In another exemplary embodiment of the present disclosure, a solenoid pump is provided that comprises a body having a fluid inlet and a fluid outlet and a fluid conduit connecting the fluid inlet and the fluid outlet, a stationary core, a reciprocating member moveable along a longitudinal axis relative to the stationary core, the reciprocating member being configured to displace fluid from the fluid inlet to the fluid outlet, an electromagnetic coil configured to generate an electromagnetic field to move the reciprocating member along the longitudinal axis, a duckbill valve positioned between the fluid inlet and the stationary core for regulating fluid flow from the fluid inlet to the stationary core, and a poppet valve positioned between the stationary core and the fluid outlet for regulating fluid flow from the stationary core to the fluid outlet.

In another exemplary embodiment of the present disclosure, a solenoid pump is provided that comprises a body having a fluid inlet and a fluid outlet and a fluid conduit connecting the fluid inlet and the fluid outlet, a stationary core, a reciprocating member moveable along a longitudinal axis relative to the stationary core, the reciprocating member being configured to displace fluid from the fluid inlet to the fluid outlet, an electromagnetic coil configured to generate an electromagnetic field to move the reciprocating member along the longitudinal axis, and a first stop configured to engage the reciprocating member to limit movement of the reciprocating member along the longitudinal axis, the first stop including a wave spring washer and at least one of an elastomeric washer and a metal washer.

In another exemplary embodiment of the present disclosure, a solenoid pump having a fluid inlet and a fluid outlet in fluid communication with the fluid inlet is provided. The solenoid pump comprises a reciprocating member moveable along a longitudinal axis between a first position and a second position, the reciprocating member moving fluid received from the fluid inlet on towards the fluid outlet during a movement between the first position and the second position, an electromagnetic coil configured to generate an electromagnetic field to move the reciprocating member from the first position to the second position, a pole piece positioned radially outwardly from the coil for directing the electromagnetic field generated by the coil, and a pair of magnetic end caps positioned at either end of the pole piece, the pole piece and the pair of magnetic end caps cooperating to provide a substantially continuous flux path for the electromagnetic field generated by the electromagnetic coil.

In another exemplary embodiment of the present disclosure, a solenoid pump is provided that comprises a body having a fluid inlet and a fluid outlet and a fluid conduit connecting the fluid inlet and the fluid outlet, a reciprocating member moveable along a longitudinal axis between a first position and a second position, the reciprocating member being configured to move fluid received from the fluid inlet on towards the fluid outlet during a movement between the first position and the second position, an electromagnetic coil configured to generate an electromagnetic field to move the reciprocating member from the first position to the second position, a seal and a seal retention member positioned radially outwardly from the reciprocating member, a spring member positioned between the seal retention member and the seal, and a body member positioned adjacent to the seal, the spring member and the body member cooperating to bias the seal against the reciprocating member to form a radial sealing surface around at least a portion of the reciprocating member.

In another exemplary embodiment of the present disclosure, an air conditioning system is provided that comprises an evaporator, a fluid reservoir configured to collect condensate from the evaporator, and a solenoid pump coupled to the fluid reservoir for moving the condensate from the fluid reservoir to a discharge location. The solenoid pump includes a body having a fluid inlet for receiving the condensate from the fluid reservoir and a fluid outlet for providing the condensate to the discharge location, the body having a fluid conduit connecting the fluid inlet and the fluid outlet, a reciprocating member supported by the body and moveable along an axis between a first position and a second position, the reciprocating member moving fluid received from the fluid inlet on towards the fluid outlet during a movement between the first position and the second position, an electromagnetic coil configured to generate an electromagnetic field to move the reciprocating member from the first position to the second position, and a pole piece positioned radially outwardly from the coil for directing the electromagnetic field generated by the coil, the pole piece being substantially symmetrical relative to the axis to provide a substantially balanced magnetic force on the reciprocating member with respect to the axis. The air conditioning system further comprises a drive circuit for providing power to the electromagnetic coil to drive the solenoid pump.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features of the invention, and the manner of attaining them, will become more apparent and will be better understood by reference to the following description of embodiments of the disclosure taken in conjunction with the accompanying drawings, wherein:

FIG. 1 illustrates a cross-sectional view of an exemplary solenoid pump;

FIG. 2 illustrates the solenoid pump of FIG. 1 having a plunger positioned near a forward stop;

FIG. 3 illustrates exemplary magnetic flux lines for the solenoid pump of FIG. 1;

FIG. 4 illustrates an exemplary solenoid pump system for removing condensate from an HVAC system;

FIG. 5A illustrates a cross-sectional view of an exemplary solenoid pump having a soft stop with multiple washers;

FIG. 5B illustrates the solenoid pump of FIG. 5A having the plunger engaged with the soft stop;

FIG. 6 illustrates an exemplary wave spring washer of the soft stop of FIGS. 5A and 5B;

FIG. 7 illustrates a cross-sectional view of the soft stop of the solenoid pump of FIGS. 5A and 5B in an exemplary compressed position;

FIG. 8 illustrates a cross-sectional view of the soft stop of the solenoid pump of FIGS. 5A and 5B in another exemplary compressed position;

FIG. 9 illustrates a cross-sectional view of another exemplary solenoid pump;

FIG. 10 illustrates a cross-sectional view of a portion of the solenoid pump of FIG. 9;

FIGS. 11A and 11B illustrate an exemplary ramped seal of the solenoid pump of FIG. 9;

FIG. 12 illustrates an exemplary magnetic force curve of the solenoid pump of FIG. 9;

FIG. 13 illustrates exemplary magnetic flux lines for the solenoid pump of FIG. 9;

FIG. 14 illustrates an exemplary pole piece of the solenoid pump of FIG. 1; and

FIG. 15 illustrates another exemplary solenoid pump system including a control switch for activating a solenoid pump.

Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE DRAWINGS

For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings, which are described below. The embodiments disclosed below are not intended to be exhaustive or limit the invention to the precise form disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may utilize their teachings. It will be understood that no limitation of the scope of the invention is thereby intended. The invention includes any alterations and further modifications in the illustrated devices and described methods and further applications of the principles of the invention which would normally occur to one skilled in the art to which the invention relates.

Referring initially to FIG. 1, an exemplary solenoid pump 10 is shown. Solenoid pump 10 is configured to pump a fluid, illustratively a liquid such as water, from an inlet 12 to an outlet 14. Other exemplary fluids displaceable by solenoid pump 10 may include gases, other liquids, gels, liquids with suspended solids, and any other flowable materials displaceable by a pump. A fluid flow path or conduit 60 extends through the interior of solenoid pump 10 between inlet 12 and outlet 14. In the illustrated embodiment, flow path 60 is centered along a longitudinal axis 62 of solenoid pump 10. Solenoid pump 10 includes a first housing portion 24 located at a first end 16 and a second housing portion 26 located at a second end 18. First housing portion 24 includes an inlet fitting 66 sized to receive a fluid supply hose for transferring fluid from a fluid reservoir to inlet 12 of solenoid pump 10. Similarly, second housing portion 26 includes an outlet fitting 68 sized to receive a discharge hose for transferring fluid from outlet 14 of solenoid pump 10 to a discharge location. Exemplary supply hose 86 and discharge hose 88 are illustrated in FIG. 4. Illustratively, inlet fitting 66 and outlet fitting 68 include barb features that couple to supply hose 86 and discharge hose 88, respectively. Other features may be used to couple the respective hoses, such as threaded surfaces, quick connect couplings, and other exemplary coupling members. First and second housing portions 24 and 26 are illustratively made of a nonmagnetic material such as a polymer (e.g. plastic), but other suitable materials may be used. In the illustrated embodiment, the body of solenoid pump 10 is made up of several members, including first housing portion 24, second housing portion 26, a pole piece 28, and a pole extension 48.

Solenoid pump 10 includes a stationary core 20 and a moveable plunger 54. The moveable plunger 54 moves along an axis 62. In the illustrated embodiment, axis 62 is a longitudinal axis about which stationary core 20 and movable plunger 54 are centered. Core 20 includes an inlet end 74 having a first seat 70 and an outlet end 76 having a second seat 72. Solenoid pump 10 includes a cavity 64 between core 20 and plunger 54 that receives fluid from inlet 12. A fluid conduit 34 extending from inlet end 74 to outlet end 76 and in fluid communication with cavity 64 forms a portion of flow path 60. Second housing portion 26 is mounted to outlet end 76 of core 20. In the illustrated embodiment, second housing portion 26 is coupled to outlet end 76 of core 20 via a threaded interface 21. A poppet valve 36 is positioned between second seat 72 of core 20 and second housing portion 26. Poppet valve 36 includes a spring 37 engaged with an inner wall 27 of second housing portion 26 for biasing poppet valve 36 towards second seat 72. Poppet valve 36 is configured to allow fluid flow from fluid conduit 34 of core 20 to outlet 14 while substantially reducing or eliminating reverse flow from outlet 14 into fluid conduit 34.

In the illustrated embodiment, plunger 54 reciprocates along longitudinal axis 62 between a first stop 50 and a second stop 52 during operation of pump 10. In the illustrated embodiment, stops 50 and 52 coincide with the placement of o-rings. As illustrated in FIG. 1, plunger 54 includes a magnetic body portion 38 coupled to an end piece 39. In one embodiment, body portion 38 is threadably coupled to end piece 39, as illustrated in FIG. 9. End piece 39 is illustratively made of a nonmagnetic material such as a polymer (e.g. plastic), but other suitable materials may be used. End piece 39 includes a radially extending flange 41 configured to engage first and second stops 50 and 52 to limit the travel of plunger 54. Body portion 38 includes an end 56 located opposite end piece 39 and configured to be received by inlet end 74 of core 20. A spring 32 positioned between a seat 58 of body portion 38 and core 20 biases plunger 54 towards first stop 50. End 56 of plunger 54 includes a cylindrical inner surface 126 (see FIG. 2) forming an opening for receiving spring 32. Alternatively, spring 32 may be positioned in other suitable areas to bias plunger 54 towards first stop 50. In the illustrated embodiment, plunger 54 has a substantially cylindrical outer surface.

A guide 44, a seal 46, a pole extension 48, and a sleeve 30 cooperate to form a travel path for plunger 54 between stops 50 and 52. Sleeve 30 is illustratively coupled to inlet end 74 of core 20 via a threaded interface 120 (see FIG. 2). As illustrated in FIG. 2, sleeve 30 includes a cylindrical inner surface 136 forming an opening for receiving plunger 54 and core 20. Sleeve 30 is illustratively made of brass, but other suitable nonmagnetic material may also be used. Sleeve 30 cooperates with seal 46 and pole extension 48 to form a sealed encasement of the fluid pumped into cavity 64. In one embodiment, sleeve 30 is press fit against pole extension 48. Pole extension 48, illustratively coupled to first housing portion 24 via a threaded interface 132 and in sealing engagement with sleeve 30, also includes a cylindrical inner surface 138 (see FIG. 2) forming an opening for receiving plunger 54.

As illustrated in FIG. 1, guide 44 is positioned between first housing portion 24 and pole extension 48 and is configured to guide translational movement of plunger 54 along longitudinal axis 62. Guide 44 is illustratively secured with an interference fit between first housing portion 24 and pole extension 48, although guide 44 may alternatively be coupled to first housing portion 24 and/or pole extension 48. Guide 44 illustratively includes a cylindrical inner surface 140 (see FIG. 2) forming an opening for receiving plunger 54. In one embodiment, guide 44 is made of a nonmagnetic material such as a polymer (e.g. plastic), but other suitable non-magnetic materials may be used.

Seal 46, illustratively positioned intermediate guide 44 and pole extension 48, provides a sealing surface against plunger 54. In one embodiment, seal 46 is a rod seal having a split teflon ring backed by an elastomer o-ring, such as a nitrile rubber o-ring. The teflon ring provides a low friction fit with plunger 54. The nitrile elastomer o-ring serves as a radial spring to maintain a radial load on the teflon ring and consequently on plunger 54. As such, a tight, low-friction seal is maintained around plunger 54. An exemplary seal 46 is a rod seal such as the ON Profile, PTFE Rod Cap Seal available from Parker Hannifin Corporation or the Composite Seal Style CS6 available from Claron Polyseal. In one embodiment, seal 46 is a ramped seal. An exemplary ramped seal 300 is illustrated in FIGS. 9-11B and described herein.

First and second stops 50 and 52, illustratively centered along longitudinal axis 62, serve to limit the travel of plunger 54. First and second stops 50 and 52 are illustratively o-ring seals comprised of a rubber or other suitable polymer. In the illustrated embodiment, first stop 50 is coupled to first housing portion 24 and second stop 52 is coupled to guide 44. First and second stops 50 and 52 may alternatively be “hard” stops made of a plastic or metal, for example. First and second stops 50 and 52 may also be comprised of one or more washers, as described herein with reference to FIGS. 5-8.

Referring to FIG. 2, a valve 40 is positioned within plunger 54 for regulating fluid flow through flow path 60. Normally closed valve 40 is configured to open to allow pressurized fluid received from inlet 12 to flow towards fluid conduit 34 of core 20. In the illustrated embodiment, valve 40 is a duckbill valve having an outlet or mouth 42 that opens when the fluid pressure on an inlet side 134 of valve 40 is greater than the fluid pressure on an outlet side 144 of valve 40. Valve 40 includes a flange 142 received between body portion 38 and end piece 39 for retaining valve 40 within plunger 54. Valve 40 is illustratively made of a rubber or other elastomer.

As illustrated in FIGS. 1 and 2, solenoid pump 10 further includes a solenoid coil 22 positioned radially outwardly from core 20 that produces an electromagnetic (EM) field upon the introduction of electric current through coil 22. Coil 22 includes conductive wire wrapped around a cylinder 23, such as a spindle or a bobbin. An inner surface 25 of cylinder 23 defines an opening for receiving core 20 and sleeve 30. Core 20 and sleeve 30 illustratively each extend partially through the opening of coil 22. In the illustrated embodiment, outlet end 76 of core 20 extends axially outwardly from solenoid coil 22 for mounting to second housing portion 26. Similarly, sleeve 30 extends axially outwardly from solenoid coil 22 for engaging pole extension 48.

Pole piece 28 positioned radially outwardly from coil 22 is configured to concentrate and direct the electromagnetic field produced by coil 22. As illustrated in FIG. 2, pole piece 28 includes an opening 148 for receiving core 20 and an opening 146 for receiving pole extension 48, sleeve 30, and plunger 54. An exemplary pole piece 28 is illustrated in FIG. 14. In the illustrative embodiment of FIG. 14, pole piece 28 is substantially D-shaped and forms an opening 114 for receiving coil 22 and core 20. Pole piece 28 illustratively includes a U-shaped portion 110 coupled to an end portion 112. Alternatively, pole piece 28 may be comprised of a single piece structure. In one embodiment, U-shaped portion 110 and end portion 112 are each made of formed sheet metal with openings 146, 148 being stamped from the sheet metal. In the illustrated embodiment, U-shaped portion 110 and end portion 112 each include interlocks 116 mated together to form the D-shaped pole piece 28. In one embodiment, U-shaped portion 110 and end portion 112 are swaged together at interlocks 116. Pole piece 28 may have other suitable shapes that serve to direct a substantially symmetrical electromagnetic field from coil 22 towards plunger 54. For example, pole piece 28 may alternatively have a polygonal-shaped or a cylindrical-shaped cross-section in a plane perpendicular to longitudinal axis 62.

In one embodiment, pole piece 28 is made of passivated stainless steel, such as passivated 430 stainless steel. In one embodiment, pole piece 28 is made of nickel plated low carbon steel. A lock ring 78 cooperates with second housing portion 26 to lock core 20 to pole piece 28. In one embodiment, lock ring 78 has a polygon-shaped (e.g. hexagonal) inner surface configured to engage a corresponding polygon-shaped outer surface of core 20 such that lock ring 78 does not rotate relative to core 20 when threading second housing portion 26 onto core 20. In one embodiment, lock ring 78 has a threaded inner surface configured to engage a threaded outer surface of core 20.

An exemplary method of assembling solenoid pump 10 of FIGS. 1-2 includes press fitting pole extension 48 to sleeve 30 and threading core 20 into sleeve 30. Pole piece 28 is guided over coil 22 and cylinder 23, and the assembly of pole extension 48, sleeve 30, and core 20 is inserted through opening 146 of pole piece 28, through the inner opening of coil 22, and through opening 148 of pole piece 28. Lock ring 78 is pushed or threaded onto the outlet end 76 of core 20, and second housing portion 26 is threaded onto outlet end 76 of core 20 with poppet valve 36 positioned between core 20 and second housing portion 26. Plunger 54 and the remaining components are coupled to solenoid pump 10 at first end 16.

Core 20, pole piece 28, pole extension 48, and body portion 38 are illustratively made of a ferromagnetic material such as magnetic stainless steel, although other suitable magnetic materials may be used. Core 20, pole piece 28, pole extension 48, and body portion 38 cooperate to provide a substantially continuous path for directing the electromagnetic field produced by coil 22. As illustrated by exemplary magnetic flux lines 100 of FIG. 3, the electromagnetic field generated by an energized coil 22 travels along a substantially continuous flux path as defined by core 20, pole piece 28, pole extension 48, and body portion 38.

In the illustrated embodiment, core 20, pole piece 28, pole extension 48, and body portion 38 are substantially symmetrical with respect to longitudinal axis 62 such that the magnetic forces on plunger 54 generated by coil 22 are substantially balanced relative to longitudinal axis 62. As such, plunger 54 is configured to travel smoothly along longitudinal axis 62 while encountering limited friction against its travel path. Balancing the magnetic forces on plunger 54 may lead to quieter operation and higher efficiency due to the reduction of off-axis energy and transverse magnetic forces, for example.

The forces involved in the movement of plunger 54 may depend on inertia, gravity, friction, viscous damping, magnetic attraction (i.e. from coil 22), and spring loads (i.e. from spring 32). By providing a substantially symmetrical core 20, pole piece 28, pole extension 48, and body portion 38 with respect to longitudinal axis 62, many of these forces acting on plunger 54 are either axial or substantially symmetrical with respect to axis 62. In one embodiment, the mass of plunger 54 is substantially small such that the gravitational force on plunger 54 is substantially negligible, as compared to the other forces acting on plunger 54. Solenoid pump 10 may be positioned in any suitable orientation, including a vertical or a horizontal orientation. An exemplary range of forces acting on plunger 54 for a vertically-oriented solenoid pump 10 are illustrated in Table 1 below. The magnitude of most forces acting on plunger 54, including inertia, friction, viscous damping, magnetic attraction, and spring load forces, are time and position dependent, i.e., dependent on the position of plunger 54 in its travel path and the length of time the solenoid pump 10 has operated. With the illustrated design of solenoid pump 10, these forces on plunger 54 are axial or substantially symmetrical with respect to longitudinal axis 62.

TABLE 1 Exemplary Range of Forces Acting on Plunger 54 Minimum Force Maximum Force (in Newtons) (in Newtons) Inertia 0 11.25 Gravity 0 0.052 Friction 0 0.016 Viscous Damping 0 1.0 Magnetic attraction 0 11.5 Spring Load 0 6.9

Pole extension 48 is configured to substantially reduce or eliminate magnetic gaps in the flux path between pole piece 28 and body portion 38 of plunger 54. As illustrated in FIGS. 1-3, pole extension 48 provides a continuous flux path between pole piece 28 and body portion 38 by bridging the electromagnetic field between pole piece 28 and body portion 38. Sleeve 30, illustratively made of a nonmagnetic material, is positioned such that it does not interrupt the continuous flux path formed by pole extension 48 and body portion 38. Similarly, core 20 and pole piece 28 are immediately adjacent to one another at an interface 102 (see FIG. 3) to allow the electromagnetic field to travel easily between core 20 and pole piece 28. In one embodiment, lock ring 78, made of a magnetic material, further cooperates with core 20 and pole piece 28 to bridge the magnetic flux traveling between core 20 and pole piece 28.

Referring to FIGS. 2 and 3, the gap 128 between end 56 of plunger 54 and inlet end 74 of core 20 is minimized to facilitate bridging the magnetic flux between plunger 54 and core 20. End 56 includes a tapered outer surface 124 configured to cooperate with a tapered inner surface 122 of inlet end 74 of core 20. In one embodiment, tapered inner surface 122 and tapered outer surface 124 are each tapered at angle of about five degrees relative to longitudinal axis 62, although tapered inner surface 122 and tapered outer surface 124 may be tapered at other suitable angles. The angled interface between end 56 of plunger 54 and inlet end 74 of core 20 allows the electromagnetic field to transition smoothly from plunger 54 to core 20, as illustrated by flux lines 100 of FIG. 3. Further, the angled interface between end 56 and inlet end 74 and the location of spring 32 within inner surface 126 of end 56 allows gap 128 to reduce in size as plunger 54 approaches second stop 52. As such, gap 128 is minimized throughout the travel of plunger 54.

In one exemplary embodiment, solenoid pump 10 is used to remove condensate water from an HVAC (heating, ventilating, and air conditioning) system. As illustrated in FIG. 4, a reservoir 84 collects condensate water 96 from an evaporator 80 of HVAC system 82. A supply hose 86 and a discharge hose 88 are coupled to inlet fitting 66 and outlet fitting 68 of solenoid pump 10, respectively. Solenoid pump 10 is configured to pump condensate water 96 provided by supply hose 86 from reservoir 84 and to discharge the condensate water 96 through discharge hose 88 to a discharge location 90. Exemplary discharge locations 90 include a floor drain or the ground.

Solenoid pump 10 is driven by a drive circuit 92 coupled to solenoid coil 22. In the illustrated embodiment, drive circuit 92 includes an AC current source for energizing solenoid coil 22. In one embodiment, a half-wave rectified AC current signal is generated by drive circuit 92, each cycle providing a one-sided sinusoidal pulse followed by a dwell of half a cycle. See, for example, exemplary current signal 94 of FIG. 4. In one embodiment, an AC current signal of about 75 milliamps at 50 or 60 Hertz is provided by drive circuit 92 to coil 22, although other suitable current signals may be used. In one embodiment, each half cycle of the AC current signal is approximately 8-10 milliseconds. In another embodiment, a frequency divider may be incorporated in drive circuit 92 to reduce the frequency of the AC current signal that energizes coil 22. For example, the frequency divider may be configured to reduce the frequency of the AC current signal to a frequency ranging from about 10 Hz to 60 Hz. Drive circuit 92 may alternatively provide a DC current signal, such as a DC square wave, for driving solenoid pump 10.

Solenoid pump 10 may be used in other systems and applications, including in household appliances such as drink dispensing devices and steam devices, for example. As illustrated in FIG. 15, a system 170 includes solenoid pump 10 driven by drive circuit 92 and coupled to a fluid reservoir 152 containing a fluid 154. Upon activation of a control switch 150, drive circuit 92 energizes coil 22 and causes solenoid pump 10 to pump fluid 154 to a discharge location 156. In one embodiment, system 170 is a coffee machine wherein solenoid pump 10 delivers coffee 154 to a discharge location 156, e.g. a user's cup or container, upon activation of switch 150. Solenoid pump 10 may also deliver water to a heating chamber of the coffee machine or to a container holding coffee grounds. In another embodiment, system 170 is a steam iron wherein solenoid pump 10 delivers distilled water 154 to a discharge location 156, e.g. heating elements in the steam iron, upon activation of switch 150. In another embodiment, system 170 is a soft drink dispenser wherein solenoid pump 10 delivers a fluid component 154, such as water or a flavoring agent, of the soft drink to a discharge location 156 upon activation of switch 150. For example, solenoid pump 10 may deliver water or a flavoring agent to a mixing chamber of the soft drink dispenser. Solenoid pump 10 may also deliver a mixed soft drink to a dispenser for dispensing into a user's container or cup. In another embodiment, system 170 is a heat exchanger wherein solenoid pump 10 pumps intermediate fluids 154 such as antifreeze mixtures or special coolants through the heat exchange system. Other exemplary systems 170 include a humidifier, a marine bilge pump, an automatic hand soap dispenser, a medical metering pump, ornamental fountains/waterfalls, etc.

In operation, plunger 54 is initially at a resting position biased away from second stop 52 by spring 32 when coil 22 is not energized, as illustrated in FIG. 1. Mouth 42 of valve 40 may be closed initially due to fluid pressure within cavity 64. When the drive current 94 from drive circuit 92 energizes coil 22, coil 22 generates an electromagnetic field that attracts plunger 54 towards core 20. The strength of the electromagnetic field generated by coil 22 overcomes the opposing spring force of spring 32 to cause plunger 54 to move towards core 20 along longitudinal axis 62. As described above, the flux path provided by pole piece 28, pole extension 48, body portion 38, and core 20 causes the electromagnetic field to produce a substantially uniform magnetic force on plunger 54. The symmetry of pole piece 28 and pole extension 48 with respect to longitudinal axis 62 causes the magnetic forces on plunger 54 to be substantially balanced along longitudinal axis 62. As such, the friction between plunger 54 and the inner surfaces of the surrounding components, including inner surface 136 of sleeve 30 and inner surface 138 of pole extension 48, is reduced, allowing plunger 54 to travel smoothly between first and second stops 50 and 52.

As plunger 54 moves towards core 20, as illustrated in FIG. 2, fluid within cavity 64 is forced through fluid conduit 34 of core 20. Seal 46 provides a sealing surface against plunger 54 to reduce or prevent fluid from cavity 64 from leaking past seal 46. The resulting increased fluid pressure within fluid conduit 34 forces poppet valve 36 to open, causing fluid to flow through outlet 14. When the force of fluid pressure within fluid conduit 34 becomes less than the opposing spring force of spring 37, poppet valve 36 is forced back towards second seat 72 of core 20 to reduce or prevent reverse fluid flow from outlet 14 to fluid conduit 34.

As coil 22 is de-energized (e.g. during the half cycle dwell of the current signal), the magnetic forces on plunger 54 are removed. As a result, spring 32 and the fluid pressure within cavity 64 pushes plunger 54 back towards first stop 50. When the pressure level on outlet side 144 of valve 40 drops below the pressure level on inlet side 134 of valve 40, mouth 42 of valve 40 opens to allow fluid from inlet 12 into cavity 64. In one embodiment, mouth 42 of valve 40 opens as plunger 54 reaches the end of travel towards second stop 52. The volume of fluid within cavity 64 increases as fluid flows through mouth 42. As plunger 54 moves toward first stop 50, mouth 42 remains open until plunger 54 slows and reverses its travel and the fluid pressure at outlet side 144 of valve 40 becomes greater than the fluid pressure at inlet side 134 of valve 40. In one embodiment, mouth 42 of valve 40 closes as plunger 54 reaches the end of travel towards first stop 50. As coil 22 is re-energized, the electromagnetic field again draws plunger 54 towards core 20 to force the fluid within cavity 64 past poppet valve 36 and through outlet 14.

In the illustrated embodiment, the electromagnetic field generated by coil 22 generally exerts a greater magnetic force on plunger 54 as plunger 54 moves away from core 20. As described herein, this greater magnetic force towards the back end of travel of plunger 54 is configured to counter an increasing average fluid pressure within cavity 64 to draw plunger 54 back towards core 20. In one embodiment, a positive head pressure builds downstream of solenoid pump 10 as fluid is pumped through solenoid pump 10. As the downstream head pressure increases, solenoid pump 10 must generate an increasing counter pressure within cavity 64 to overcome the increasing head pressure at outlet 14 to force open poppet valve 36 and move fluid into the discharge. As such, the average fluid pressure within cavity 64 rises with the increasing downstream head pressure. In one embodiment, the fluid pressure within cavity 64 during operation of pump 10 ranges from a low pressure substantially equal to the pressure at inlet 12 to a high pressure substantially equal to the discharge pressure at outlet 14. Accordingly, the average (time-dependent) pressure within cavity 64 rises during operation of solenoid pump 10 and becomes a force that pushes back on plunger 54, thereby reducing the travel distance of plunger 54 during each pump cycle. As a result, a greater magnetic force from coil 22 is required to counter this increasing average pressure within cavity 64 to attract plunger 54 back towards core 20. In one embodiment, the solenoid pump 10 is configured to generate an increasing magnetic force on plunger 54 as gap 128 increases in size, i.e. as plunger 54 moves further away from core 20.

In one embodiment, during periods of low average pressure within cavity 64 (e.g. when solenoid pump 10 starts operation), plunger 54 contacts second stop 52 during the pumping cycle but does not contact first stop 50 during the pumping cycle. In particular, plunger 54 is pulled forward towards second stop 52 before reaching the back end of travel against first stop 50. As the downstream head pressure increases and the average pressure builds in cavity 64, plunger 54 may no longer reach second stop 52 during each pumping cycle and may be forced more and more against first stop 50. Accordingly, a greater magnetic force at the back end of the stroke of plunger 54 allows solenoid pump 10 to increase flow at low pressures in cavity 64 and to continue to draw plunger 54 towards core 20 even at high pressures within cavity 64.

In the illustrated embodiment, spring 32 acts on plunger 54 for a portion of the entire travel range of plunger 54 between first stop 50 and second stop 52. Spring 32 provides resistance against plunger 54 during the forward travel (from first stop 50 to second stop 52) to reduce the impact of plunger 54 against second stop 52. Spring 32 also improves the backwards response of plunger 54 by forcing plunger 54 to start moving backwards towards first stop 50 more quickly after reaching the end of forward travel towards second stop 52. As plunger 54 nears first stop 50, spring 32 is no longer engaged with plunger 54. As such, spring 32 illustratively does not act on plunger 54 throughout the entire range of travel of plunger 54.

As illustrated in FIG. 1, a gap exists between seat 58 and spring 32 when plunger 54 is positioned against first stop 50. Engagement of spring 32 with plunger 54 throughout the entire travel range of plunger 54 would require additional current through coil 22 in order to generate enough magnetic force to overcome the opposing spring force at the back end of the stroke of plunger 54 (near first stop 50), for example. In one embodiment, spring 32 is also detached from first seat 70 of core 20. Due to the fluid resistance of spring 32 to motion and inertia, spring 32 is illustratively forced downstream against first seat 70 throughout the operation of solenoid pump 10.

Referring to FIGS. 5-6, exemplary first and second stops 50 and 52 of solenoid pump 10 are shown according to one embodiment. In the illustrated embodiment, second stop 52 includes a wave spring washer 202, an intermediate washer 204, and an elastomeric washer 206. Second stop 52 is illustratively mounted to a backing washer 200. Backing washer 200 is coupled between pole extension 48 and guide 44 and adjacent to seal 46. In the illustrated embodiment, seal 46 forms a sealing surface against backing washer 200. In one embodiment, a seal is formed between backing washer 200 and guide 44.

Wave spring washer 202, or “wavy washer”, is positioned between backing washer 200 and intermediate washer 204. Wave spring washer 202 provides an axial spring force when compressed while requiring minimal axial space. The curved geometry of wave spring washer 202 creates a plurality of openings between backing washer 200 and intermediate washer 204. See, for example, openings 220 of exemplary wave spring washer 202 in FIG. 6. Openings 220 allow fluid to pass through wave spring washer 202. The exemplary wave spring washer 202 of FIG. 6 includes multiple wavy washers coupled together to provide a greater axial force. However, wave spring washer 202 may be comprised of a single wavy washer. In the illustrated embodiment, elastomeric washer 206 is sealingly coupled to intermediate washer 204. Elastomeric washer 206 provides a seal against flange 41 of plunger 54 when plunger 54 engages second stop 52. Washers 200-206 are each illustratively disk-shaped. Backing washer 200 and intermediate washer 204 are illustratively comprised of stainless steel, although other suitable materials may be used. Wave spring washer 202 may be made of stainless steel, high carbon steel, or another suitable material.

Second stop 52 is illustratively a “soft” stop that compresses upon engagement by plunger 54 to thereby absorb some of the energy from the impact of plunger 54. The compression of second stop 52 is attributable to the slight compression of elastomeric washer 206 as well as the deflection of wave spring washer 202. In particular, the engagement of plunger 54 with elastomeric washer 206 forces wave spring washer 202 to compress between intermediate washer 204 and backing washer 200. In one exemplary embodiment, wave spring washer 202 has a free (unloaded) height of about 0.035 inches and a height of about 0.015 inches when deflected to load. Exemplary wave spring washers 202 are the wave spring washer, Model No. W0492, and the multiwave compression spring, Model No. MW0375, each available from Associated Spring Raymond located in Maumee, Ohio.

First stop 50 is also illustratively a “soft” stop that compresses upon engagement by plunger 54 to thereby absorb some of the energy from the impact of plunger 54. The multiple washer design of second stop 52 illustrated in FIGS. 5-8 may also be utilized for first stop 50 with an intermediate washer 210 positioned between an elastomeric washer 208 and a wave spring washer 212. Alternatively, first stop 50 may be comprised of an intermediate washer 210 positioned between two wave spring washers. Similar to intermediate washer 204, intermediate washer 210 is also illustratively made of stainless steel.

In operation, plunger 54 is initially spaced apart from second stop 52, as illustrated in FIG. 5A. As plunger 54 moves towards core 20, elastomeric washer 206 of second stop 52 contacts and forms a seal with the surface of flange 41 of plunger 54, as illustrated in FIG. 5B. A cavity 230 is formed upon engagement of plunger 54 with elastomeric washer 206. As second stop 52 compresses due to the engagement with plunger 54, the fluid pressure within cavity 230 increases. Fluid within cavity 230 is thereby forced through openings 220 (see FIG. 6) of wave spring washer 202, as illustrated by arrows 232 in FIGS. 7 and 8. Referring to FIG. 7, the impact of plunger 54 causes wave spring washer 202 to compress to first height H1. As the force of plunger 54 continues to compress second stop 52, wave spring washer 202 may be further deflected to load at a second height H2, illustrated in FIG. 8. In one embodiment, first height H1 is about 0.025 inches, and second height H2 is about 0.015 inches, for example. In one embodiment, wave spring washer 202 has a free, unloaded height of about 0.035 inches. In one embodiment, second height H2 is about 40% of the free (unloaded) height of wave spring washer 202.

The stiffness of second stop 52 is dependent on the velocity of plunger 54. As second stop 52 compresses, more and more fluid within cavity 230 must escape through openings 220 of wave spring washer 202. If plunger 54 hits second stop 52 at a first, slow velocity, second stop 52 compresses at a first, slow rate, allowing the fluid within cavity 230 to move through openings 220 of wave spring washer 202 relatively easily. Because the fluid within cavity 230 is able to escape, the fluid pressure within cavity 230 is relatively low, and the stiffness of second stop 52 is relatively soft. If plunger 54 hits second stop 52 at a second, higher velocity, second stop 52 compresses at a second, faster rate, causing openings 220 of wave spring washer 202 and cavity 230 to quickly reduce in size. As a result, the fluid pressure within cavity 230 quickly increases as the fluid within cavity 230 tries to escape, leading to a relatively stiff second stop 52.

The stiffness of second stop 52 is also dependent on the mass of plunger 54 and the combined mass of second stop 52. A greater mass of plunger 54 will result in a “harder” stop due to the greater impact on second stop 52 and the resulting quicker compression of second stop 52. Similarly, a greater combined mass of wave spring washer 202, intermediate washer 204, and elastomeric washer 206 provides a greater inertial resistance against the impact of plunger 54. This “inertial damping” provided by a relatively large mass second stop 52 and a relatively low mass plunger 54 results in a “softer” second stop 52. Further, the geometry of guide 44 and of the components of second stop 52 determines the size and tightness of the flow paths between guide 44 and second stop 52 and through openings 220 of wave spring washer 202. Smaller flow paths restrict and slow the fluid escaping from cavity 230, resulting in a harder second stop 52. Accordingly, a variety of stiffness profiles of second stop 52 may be achieved by tailoring the geometries of plunger 54, guide 44, and the components of second stop 52. In the same way, a variety of stiffness profiles of first stop 50 may also be achieved. A standard wire compression spring may alternatively be utilized in first and second stops 50 and 52 instead of a wave compression spring.

Referring to FIG. 9, another exemplary solenoid pump 10′ is illustrated. Pole piece 28 of FIG. 9 is positioned between pole extension 48 and lock ring 78. Pole extension 48 and lock ring 78 are illustratively magnetic end caps positioned at either end of pole piece 28. Pole piece 28 is substantially symmetrical in shape. In the illustrated embodiment, the walls of pole piece 28 are substantially flat. In one embodiment, pole piece 28 is substantially cylindrical or tubular in shape. Pole extension 48 is illustratively coupled to the outside wall of first housing portion 24 via a threaded interface 314 and to sleeve 30 via a threaded interface 312. As illustrated in FIGS. 9 and 9A, pole extension 48 and lock ring 78 are shaped to substantially reduce or eliminate magnetic gaps in the flux path between the pole piece 28, body portion 38 of plunger 54, and core 20. Pole extension 48 provides a substantially continuous flux path between pole piece 28 and body portion 38 by bridging the electromagnetic field between pole piece 28 and body portion 38. Sleeve 30 is positioned such that it does not interrupt the continuous flux path formed by pole extension 48 and body portion 38. Similarly, lock ring 78 provides a substantially continuous flux path between pole piece 28 and core 20 by bridging the electromagnetic field between pole piece 28 and core 20. As illustrated by exemplary magnetic flux lines 400 of FIG. 13, the electromagnetic field generated by an energized coil 22 travels along a substantially continuous flux path as defined by core 20, lock ring 78, pole piece 28, pole extension 48, and body portion 38.

The combination of pole piece 28, pole extension 48, and lock ring 78 serve to amplify the magnetic attraction forces generated by coil 22. As such, coil 22 of solenoid pump 10′ may require less current while maintaining strong magnetic forces on plunger 54. Further, the combination of pole piece 28, pole extension 48, and lock ring 78 may allow for a lower inertia plunger 54.

Solenoid pump 10′ of FIG. 9 further includes a washer 304 and a washer 306. Washer 304 is positioned between inlet end 74 of core 20 and sleeve 30. Washer 304 provides a “final” stop to limit the travel of plunger 54 as plunger 54 compresses second stop 52 and moves towards core 20. Washer 304 is adapted to engage a shoulder 316 of plunger 54 when flange 41 of plunger 54 fully or nearly fully compresses second stop 52. In one embodiment, washer 304 has a height or thickness of approximately 0.035 inches.

Washer 304 stops plunger 54 from moving into direct or close engagement with core 20. The magnetic attraction forces between plunger 54 and core 20 would increase greatly if plunger 54 were configured to move substantially close to core 20 and/or into contact with core 20. Washer 304 limits the forward travel of plunger 54 towards core 20 to reduce the effects of these stronger magnetic attraction forces. In addition, residual magnetism increases as plunger 54 moves close to core 20. If plunger 54 contacts or moves substantially close to core 20 during pump operation, residual magnetism may hold plunger 54 and core 20 together after the removal of current from coil 22, despite the opposing forces of spring 32 and fluid pressure within cavity 64. Accordingly, washer 304 reduces the effects of residual magnetism and reduces the noise of operation of solenoid pump 10′.

Washer 306 is illustratively positioned between poppet valve 36 and inner wall 27 of second housing portion 26. Washer 306 serves as a fluid seal between core 20 and second housing portion 26. Washer 304 and washer 306 are illustratively elastomeric washers, although other suitable materials may be used.

As illustrated in FIG. 9, coil 22 is wound on a bobbin 308 positioned between pole extension 48 and lock ring 78. Coil 22 is received between opposing flanges 320 of bobbin 308. In one embodiment, bobbin 308 is substantially cylindrical in shape. Bobbin 308 is illustratively press fit between pole extension 48 and lock ring 78. In the illustrated embodiment, a washer 310 is positioned between bobbin 308 and lock ring 78 to serve as a spacer biasing bobbin 308 towards pole extension 48. Washer 310 is illustratively a wave spring washer, although other suitable washers may be used.

As illustrated in FIGS. 9 and 10, second stop 52 is coupled to a seal retainer 318 positioned between first housing portion 24 and pole extension 48. In one embodiment, seal retainer 318 is comprised of a rigid material such as a plastic or other rigid polymer. In one embodiment, seal retainer 318 is comprised of magnetic stainless steel and provides a substantially continuous flux path between pole extension 48 and body portion 38 of plunger 54 by bridging the electromagnetic field between pole extension 48 and body portion 38, as illustrated by exemplary magnetic flux lines 400 in FIG. 13. A ramped seal 300 is positioned adjacent to pole extension 48 and around plunger 54. Ramped seal 300, like seal 46 of FIG. 1, provides a low-friction, sealing surface against plunger 54. In one embodiment, ramped seal 300 is made of a fluorocarbon-based material such as a fluoropolymer. Ramped seal 300 provides a low friction fit with plunger 54. A spring washer 302, illustratively a wave spring washer, is positioned between seal retainer 318 and ramped seal 300. In the illustrated embodiment, ramped seal 300 and spring washer 302 are press fit between seal retainer 318 and pole extension 48.

As illustrated in FIGS. 11A and 11B, ramped seal 300 includes a substantially cylindrical inner surface 334 defining an opening 340 for receiving plunger 54. Ramped seal 300 further includes a tapered outer surface 330 extending between a first end 342 and a second end 344. First end 342 illustratively includes a shoulder 332 extending perpendicular to a longitudinal axis of ramped seal 300. Second end 344 illustratively includes an edge 336 extending parallel to a longitudinal axis of ramped seal 300.

The circumference of ramped seal 300 includes a gap or break 338. As such, ramped seal 300 may be molded slightly larger than the outer diameter of plunger 54, allowing ramped seal 300 to slide onto plunger 54 with relative ease during assembly of solenoid pump 10′. Gap 338 illustratively includes a winding, labyrinth path extending from first end 342 to second end 344 of ramped seal 300. Spring washer 302 (see FIGS. 9 and 10) compresses ramped seal 300 against a tapered wall 322 of pole extension 48. As ramped seal 300 is compressed axially into place, the engagement of tapered outer surface 330 with corresponding tapered wall 322 of pole extension 48 squeezes the circumference of ramped seal 300 to create a seal around plunger 54. As ramped seal 300 is squeezed around plunger 54, gap 338 reduces in size. The narrow, labyrinth path through gap 338 provides a viscous seal through gap 338. In one embodiment, an absolute seal is not provided through gap 338. In the illustrated embodiment, the tight, flat seal between ramped seal 300 and plunger 54 and the narrow, labyrinth path through gap 338 serve to block most fluid from flowing past ramped seal 300 while reducing drag on plunger 54. In one embodiment, ramped seal 300 stops 90% or more of the fluid from passing through during the forward cycle of plunger 54.

Referring to FIG. 12, an exemplary magnetic force curve 350 for solenoid pump 10′ of FIGS. 9 and 10 is shown. As illustrated, when gap 128 between plunger 54 and core 20 is small (i.e., when plunger 54 is positioned near second stop 52 and the back pressure within cavity 64 is relatively low), the magnetic force on plunger 54 is strong enough to draw plunger 54 closer to second stop 52. As the back pressure within cavity 64 builds, plunger 54 is pushing against an increasingly large counter force. As described above, plunger 54 begins using the back part of its range of travel during each pumping cycle, resulting in an increase in gap 128. As illustrated by magnetic force curve 350, solenoid pump 10′ is configured to produce a greater magnetic force on plunger 54 as gap 128 increases in size. Accordingly, plunger 54 has more energy to push against the counter pressure (i.e., the fluid pressure within cavity 64), thereby enabling solenoid pump 10′ to acquire a higher pumping pressure and a higher flow. In contrast, a curve 352 of FIG. 12 illustrates an exemplary prior art pump design where the magnetic forces on the plunger decrease as the gap between the plunger and the stationary core increases.

In one embodiment, pole piece 28 of solenoid pump 10′ is constructed using a constrained layer damping design (e.g. dual metal laminate) to absorb vibrations in pole piece 28 and to reduce the operating noise of solenoid pump 10′. In particular, pole piece 28 may be constructed of two or more steel or metal layers with a viscoelastic bonding material applied between the layers. In one embodiment, the layers are metal laminates. An exemplary viscoelastic material is a viscoelastic damping polymer such as Model Nos. 110-, 112-, and 130-available from 3M Company. The shear stresses developed between the steel or metal layers may be transferred into thermal energy in the viscoelastic material, thereby dampening vibration and reducing noise in the device.

An exemplary method of assembling solenoid pump 10′ of FIG. 9 includes threading sleeve 30 onto core 20 with washer 304 positioned therebetween. Pole extension 48 is threaded onto sleeve 30, and the coil 22/bobbin 308 assembly is guided over the outer diameter of the assembly of pole extension 48, sleeve 30, and core 20. Pole piece 28 is guided over coil 22 and bobbin 308, and lock ring 78 is slipped over the outlet end of core 20 with a tight slip fit. Second housing portion 26 is threaded onto core 20 with poppet valve 36 positioned between core 20 and second housing portion 26. Plunger 54 and the remaining components are coupled to solenoid pump 10′ at the inlet end.

While this invention has been described as having an exemplary design, the present invention may be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains. 

1. A solenoid pump comprising: a body having a fluid inlet and a fluid outlet and a fluid conduit connecting the fluid inlet and the fluid outlet; a reciprocating member supported by the body and moveable along an axis between a first position and a second position, the reciprocating member moving fluid received from the fluid inlet on towards the fluid outlet during a movement between the first position and the second position; an electromagnetic coil configured to generate an electromagnetic field to move the reciprocating member from the first position to the second position; and a pole piece positioned radially outwardly from the coil for directing the electromagnetic field generated by the coil, the pole piece being substantially symmetrical relative to the axis to provide a substantially balanced magnetic force on the reciprocating member with respect to the axis.
 2. The solenoid pump of claim 1, further comprising a pole extension positioned at least partially between the pole piece and the reciprocating member, the pole extension bridging the electromagnetic field between the pole piece and the reciprocating member.
 3. The solenoid pump of claim 2, further comprising a stationary core positioned at least partially within the electromagnetic coil and having a fluid conduit in fluid communication with the fluid inlet and the fluid outlet.
 4. The solenoid pump of claim 3, wherein the reciprocating member, the pole piece, the pole extension, and the stationary core are made of stainless steel.
 5. The solenoid pump of claim 3, further comprising a first valve positioned within a cavity of the reciprocating member and a second valve positioned between the stationary core and the fluid outlet, the first valve and the second valve cooperating to regulate the flow of fluid from the fluid inlet to the fluid outlet.
 6. The solenoid pump of claim 5, wherein the first valve is a duckbill valve and the second valve is a poppet valve.
 7. The solenoid pump of claim 3, further comprising a seal providing a radial sealing surface around the circumference of the reciprocating member, the reciprocating member being movable relative to the seal.
 8. The solenoid pump of claim 7, wherein the seal is one of a rod seal and a ramped seal.
 9. The solenoid pump of claim 7, further comprising a sleeve positioned between the stationary core and the pole extension and received within the electromagnetic coil, the sleeve cooperating with the pole extension and the seal to form a sealed travel path for the reciprocating member.
 10. The solenoid pump of claim 3, further comprising a first stop and a second stop each configured to limit the travel of the reciprocating member, the first stop limiting movement of the reciprocating member away from the stationary core and the second stop limiting movement of the reciprocating member towards the stationary core.
 11. The solenoid pump of claim 10, wherein the first and second stops each include a wave spring washer and at least one of an elastomeric washer and a metal washer.
 12. The solenoid pump of claim 10, wherein the reciprocating member includes a magnetic body portion coupled to a nonmagnetic end piece, the end piece including a flanged portion for engaging the first and second stops.
 13. The solenoid pump of claim 10, further comprising a washer coupled between the stationary core and the reciprocating member and configured to cooperate with the second stop to limit movement of the reciprocating member towards the stationary core.
 14. The solenoid pump of claim 10, further comprising a spring positioned between the stationary core and the reciprocating member for biasing the reciprocating member towards the first stop.
 15. The solenoid pump of claim 14, wherein the solenoid coil is energized by a half-wave rectified AC current signal, wherein when the solenoid coil is energized the electromagnetic field pulls the reciprocating member towards the stationary core and when the solenoid coil is de-energized the spring pushes the reciprocating member away from the stationary core.
 16. The solenoid pump of claim 3, wherein the reciprocating member includes an end having a tapered outer surface and the stationary core includes a receiving end having a tapered inner surface configured to cooperate with the tapered outer surface of the reciprocating member, wherein the end of the reciprocating member is received within the receiving end of the stationary core as the reciprocating member moves towards the stationary core.
 17. The solenoid pump of claim 16, wherein the end of the reciprocating member includes an inner opening for receiving a spring, the spring extending between the end of the reciprocating member and the receiving end of the stationary core for biasing the reciprocating member away from the stationary core.
 18. The solenoid pump of claim 1, wherein the pole piece is constructed of a plurality of metal layers and a viscoelastic bonding material coupled to at least one of the metal layers.
 19. The solenoid pump of claim 1, wherein the solenoid pump is configured to move a heat exchange fluid through a heat exchange system.
 20. The solenoid pump of claim 1, wherein the solenoid pump is configured to deliver water to a heating element of a steam device.
 21. The solenoid pump of claim 1, wherein the solenoid pump is configured to advance a drink product towards a dispenser of a drink dispensing device.
 22. The solenoid pump of claim 1, wherein the solenoid pump is configured to provide water to a chamber of a coffee machine. 23-51. (canceled) 